‘Haywire” is a wannabe, or rather a wanna-B, and that B is for “Bourne.” As each imitator comes and (rapidly) goes, my appreciation for the best superspy franchise deepens. Even top directors — in this case Steven Soderbergh — can’t figure out the trick.

If you don’t mind a baffling plot, unexplored characters and a so-what ending, though, the movie is watchable thanks to Soderbergh’s skittery flair and some ace dialogue.

A mixed martial arts fighter named Gina Carano gets her first starring role as Mallory, an undercover assassin, and does not waste the opportunity. Considerably sexier than the typical stalk of celery that passes for a she-killer these days, she deploys icy glances and fast moves with the verve of Jennifer Lopez in “Out of Sight.” (Lopez’s subsequent career proved that, like most performers, she can easily be non-excellent in non-Soderbergh movies.)

A prologue at a diner in snowy upstate New York leads to a confrontation with a fellow spook (Channing Tatum) and a long drive with a helper/hostage (Michael Angarano). Naturally Mallory tells this random stranger everything about her secret back story involving missions in Barcelona and Dublin. Angarano is merely comic relief who never does anything funny, as well as a really awkward method for delivering exposition to the audience. When he’s off-screen, you’ll forget about him. You’ll also forget about him when he’s on-screen, since he means nothing.

As Mallory explains her trips to Spain and Ireland, I had somewhere between one-sixteenth and three-eighths of a clue what was going on. (By the time I started to get wise, the movie was 30 seconds from being over.) All we’re really supposed to know is that she’s cool, and she trusts no one except maybe her dad, a fellow ex-Marine (Bill Paxton). And what is his role? Hanging around in New Mexico, waiting for the screenplay to give him something to do, which it never quite does.

Higher-ups in Washington (Ewan McGregor, Michael Douglas) compete for Mallory’s services, occasioning some chatter that, scintillation-wise, is roughly on the level of postal regulations. There’s some blather about being on a private contract as opposed to being in the employ of the government. There’s some chin-wag about the “essential element clause” and hazardous-duty bonuses. You get the feeling someone’s going to whip out a pension-benefits chart. At least Douglas looks good and has some tart lines courtesy of writer Lem Dobbs, who in the 1990s did the fragmented thriller “The Limey.”

The point of the movie is the look of the action scenes, which have a tangy realness and a surprising patience. Long takes of, for instance, Mallory sprinting or evading cops in Dublin give you a sense of her determination, and the fights are well-choreographed. Soderbergh loathes cliché, but at times the contrarian way is also the wrong way, as when he bungles a shootout by keeping his camera safely tucked behind it.

In one of the most engaging scenes, Michael Fassbender checks in as a new teammate. (He needs “eye candy,” and when Mallory bristles, she is told, “You’re the eye” — huh?) She gets to show off her silky evening-wear, and this is one professional fighter who cleans up nice. Her ripped stockings caress thighs that, in a moment of improvisation, can be used to asphyxiate a foe. Not since Graham Chapman was executed by a flock of half-naked roller-derby girls in “Monty Python’s The Meaning of Life” was death so congenial to its victim.